This invention relates to the field of ancillaries for spinal osteosynthesis.
This invention relates particularly to an ancillary for a spinal osteosynthesis system of the type comprising at least one implant designed to be implanted in a spine, the said implant comprising accommodation means oriented approximately along an axis and designed to accommodate at least one rod type connecting element, the ancillary comprising holding means intended to cooperate with the said implant and a manipulation means free to move with respect to the said holding means, designed to enable manipulation of the said connecting element.
One of the main difficulties with this type of surgery is placement of the rod in the implants (for example of the hook or pedicular screw type). Another known difficulty is in placing the implant closing system to hold the rod in place in the implant.
Prior art includes ancillaries for spinal osteosynthesis comprising means of holding the rod in place designed to cooperate with the implant.
International patent application No. WO 01/01873 proposes making an ancillary with two spouts that fit into recesses located in the head of the implant, on each side of the accommodation means. The ancillary also comprises a device that is used to exert a force on the rod to move it laterally and/or vertically, to enable positioning of the rod in the accommodation means.
The major disadvantage of ancillaries according to prior art lies in the fact that the implant grip is unilateral, in other words the ancillary only bears on the implant with the holding grip.
The small volume of implants and the fineness of the instrument, which are compulsory for surgical reasons, make it impossible to obtain a very rigid implant grip. The thrust of the rod in the implant requires a variable force depending on the surgical situation, but when large forces are applied, the thrust induces a large torque on the implant, making the implant pivot about the end of the holding grip and possibly tearing off the grips on the implant.
There are two types of consequences; firstly, the implant may no longer be correctly positioned or may be torn off, and secondly the connecting element blocking system may no longer block the connecting element correctly.
This invention is intended to correct the disadvantages of prior art by proposing an ancillary able to distribute the forces exerted on the implant when handling the connecting element so as to minimize the influence of these forces on its positioning.
In order to achieve this, this invention is of the type described above and in its broadest acceptance it is remarkable, in that the said holding means are designed to be arranged on one side of the accommodation means and in that the said manipulation means comprises attachment means that will cooperate with the said implant on the side of the accommodation means opposite the centreline of the accommodation means.
The said manipulation means is preferably fixed removably to the said ancillary.
The said manipulation means is preferably fixed to the said ancillary using a return part enabling free rotation of the said manipulation means.
The ancillary preferably comprises at least one recess to enable the passage of a placement instrument.
The said holding means are preferably located on a lever, with at least a hollow cylindrical part to enable the passage of the said placement instrument.
The said holding means are preferably composed of jaws free to move with respect to each other.
The said attachment means are preferably composed of jaws free to move with respect to each other.
The said jaws, of the said holding means and/or the said attachment means are preferably free to move with respect to each other about a plane of symmetry.
The said hollow cylindrical part is preferably placed such that it has a centreline that passes through the said planes of symmetry of the said jaws.
This invention also relates to a process for installation of a spinal osteosynthesis system comprising at least one implant using an ancillary, the said implant comprising accommodation means arranged approximately along an axis and designed to accommodate at least one rod type connecting element, the ancillary comprising holding means designed to cooperate with the said implant, and a manipulation means free to move with respect to the said holding means, designed to enable manipulation of the said connecting element, in which the said holding means are arranged on one side of the accommodation means, in which the said connecting element is then manipulated using the said manipulation means so that the connecting element centreline is parallel to the centreline of the said accommodation means and in which the said manipulation means comprises attachment means that then cooperate with the said implant on the side of the accommodation means opposite the centreline of the accommodation means.
The said connecting element is preferably located along the centreline of the accommodation means by rotation of the said holding means about a return part.
The said connecting element is preferably located at the bottom of the accommodation means by pushing the connecting element using a placement instrument.
A closing means is then preferably positioned on the said connecting element before withdrawing the said attachment means of the manipulation means and the said holding means.
Advantageously, the ancillary according to the invention forms two clips each fitted with two levers, the two clips being connected together by a return part, the four levers being used to distribute the stresses exerted on each side of the implant, about the means accommodating the connecting element.
Also advantageously, the position of the connecting element is thus easier to make and there is less risk of bad positioning since the stresses applied to the implant are better distributed.
Furthermore, the risk of tearing off the implant is minimised, particularly when the correction applied by the connecting element to the implant once the connecting element positioned in the accommodation means, is high.
Therefore, it is easier and faster to implant an osteosynthesis system using an ancillary according to the invention.